Once a Cheater… always a Cheater?

This week a friend(let’s call her Karen) confided in me, about how one of her best friends and her boyfriend cheated on her.
Something so gutworthingly wrong, and yet people still seem to think it’s an ok thing to do.

Three of us were there discussing what had happened, another friend (let’s call her Joan), myself and the Karen.
The conversation that followed was really interesting.

It seems, that the best friend who had done the terrible deed, had now been made an outcast in that particular friendship group, and none of them considered her a friend and wanted to talk to her again.
It wasn’t only because of her being with the guy, but because she had blatantly lied about it to all of them of the incident, and still wasn’t telling the full story.
Karen believed this former friend deserved everything that she was getting, and that there was nothing she could do, to fix the situation and make any of them friends again.
She refuses to see or speak to her again.

Joan however was arguing that Karen should give the friend a chance to explain, to make amends, and to apologise.
She was defending the friend and believed that Karen and her other friends were being too harsh and should be more sympathetic about the whole situation.

I just kept my mouth shut, not knowing how I felt about it all.
It was so interesting to watch such close friends have completely different viewpoints on the same scenario.
Which stance would you take?

Outcast the friend?
or
Forgive the friend, because she feels bad and is only human?